Ethylene selective oligomerization catalyst systems and method for ethylene oligomerization using the same

Abstract

The disclosure provides a catalyst system and a method for ethylene oligomerization using this. The catalyst system contains: ligand a, containing carbene groups of imidazole ring type; transition metal compound b, that is one of IVB˜VIII group metal compounds; activator c, that is a compound containing III A group metals; the ligand a contains at least one group as shown in general formula I:in which, bridging group A contains a main chain including alkyl, alkenyl, aryl groups or the combination of them and the first heteratom; E is a linear or cyclic group containing the second heteroatom; R is a hydrocarbyl group. The catalyst system is especially used for trimerization and tetramerization of ethylene. The catalyst system has high selectivity for 1-hexene and 1-octene, low selectivity for 1-butene and 1-C10+, and the total percent content of C6˜C8 linear □α-olefin in the product is more than 90% by mass.

What is claimed is: 
     
       1. A catalyst for selective oligomerization of ethylene, comprising three components:
 a ligand, wherein the ligand comprises carbene groups of imidazole ring; 
 a transition metal compound, wherein the transition metal compound contains chromium; and 
 an activator, wherein the activator is a mixture of alkyl aluminum compound and alkyl aluminoxane compound removed of volatile components, in which the alkyl aluminum compound is triethyl aluminum and the alkyl aluminoxane compound is methyl aluminoxane removed of volatile components; 
 wherein the ligand contains at least one group as shown in general formula I as shown below; 
 
       
         
           
           
               
               
           
         
         wherein the main chain of the bridging group A is —(CH 2 ) n —SiR′R″—(CH 2 ) m (0≤n≤3, 0≤m≤3), in which R′ and R″ are each independently methyl, isopropyl, cyclohexanyl, cyclopentyl, phenyl, naphthyl or 2,6-diisopropyl phenyl, respectively; 
         the group E is a linear or cyclic group containing a second heteroatom, and the group E is selected from the group consisting of diisopropyl phosphino, dicyclohexyl phosphino, dimethyl phosphino, diethyl phosphino, diphenyl phosphino, di-o-methylbenzene phosphino, di-o-ethylphenyl phosphino, di-o-isopropylphenyl phosphino, diphenyl phosphino, dinaphthyl phosphino, methoxy, ethoxy, phenoxy, isopropoxy, methyl mercapto, ethyl mercapto, phenylmercapto, and isopropyl Mercapto; 
         R is a hydrocarbyl group. 
       
     
     
       2. The catalyst according to  claim 1 , wherein R in general formula I is selected from the group consisting of an alkyl group, a vinyl group, and an aromatic group. 
     
     
       3. The catalyst according to  claim 1 , wherein a molar ratio of the triethyl aluminum to the methyl aluminoxane removed of volatile components is 0.01-100. 
     
     
       4. The catalyst according to  claim 1 , wherein a molar ratio of ligand, the transition metal compound and the activator is 1:(0.5-100):(0.1-5000). 
     
     
       5. A method for an ethylene oligomerization reaction by carrying out the ethylene oligomerization reaction in the presence of the catalyst according to  claim 1 , comprising mixing ethylene with the catalyst.